Parents rely on the accuracy of criminal background checks to safeguard their children from possibly predatory schoolteachers or day-care workers. Consumers and employers trust them to ferret out dishonest real estate agents, car sellers and and job seekers.

But the near failure of one background check to unearth information that proved critical in a recent high-profile adoption dispute begs the question: How reliable are these scans?

They're not foolproof, but generally -- 90 percent to 95 percent -- reliable, according to officials at Utah's Bureau of Criminal Identification (BCI), which handles an average of 4,300 to 5,500 background checks a month, mostly on applicants for professional licenses.

Background checks are easy to execute and amount to running a person's name and date of birth or fingerprint against a computer database, says Alice Erickson, who oversees the program. The bureau manages a statewide database of criminal arrests, charges and convictions fed by law enforcement agencies and the courts.

It also has access to fingerprint data in six other states: Alaska, Idaho, Montana, Wyoming, Nevada and Oregon.

But Erickson says the databases are only as trustworthy as the information they contain and the people who operate them. Also, only conviction information that would render an applicant ineligible for a job, adopting a child or other position -- mostly felonies -- is forwarded to the inquiring agency.

"Even with computers you have a margin of error," said Erickson.

Stephen Kusaba and Lenna Habbeshaw appear to have fallen within that margin.

The middle-aged couple were the prospective adoptive parents of "Baby Tamia," the now-7-month-old girl surrendered for adoption last December by a Chicago woman who later changed her mind and sued to get her back.

The custody dispute raged for months in an Illinois court before Kusaba and Habbeshaw were arrested in March for allegedly possessing cocaine, marijuana and drug paraphernalia. Soon after, an Illinois judge overturned the adoption on an unrelated technicality.

But the arrest brought to light previous drug convictions that, had Kusaba not revealed himself, would never have surfaced in his background check.

In applying to adopt a child through Midvale-based A Cherished Child Adoption Agency, Kusaba and Habbeshaw underwent criminal work-ups, as do all Utah adoptive parents. They also were screened against a database of child abuse offenders.

Prospective parents are rejected if their histories show any felony offense, or misdemeanors and infractions that qualify as sex crimes or crimes against a person, such as domestic violence, assault and battery.

Misdemeanor drug offenses don't automatically disqualify a parent, but trigger a secondary review that involves a five-person board of Human Services officials, which looks at the circumstances of the crime and remedial steps the parent may have taken -- assuming the state knows about them.

Derek Williams, an attorney for A Cherished Child, says had Kusaba not admitted on his application that in 1991 he had pleaded guilty to two Class A misdemeanor counts of attempting to possess drugs, "they probably wouldn't have gotten a hit."

Following this disclosure, the state Human Services department, which determines whether parents are fit to adopt, ordered a more thorough scan against the Federal Bureau of Investigation database in Clarksburg, W.V.

A review committee cleared Kusaba as posing no risk to children, said state Licensing Director Ken Stettler. "When an offense has occurred 15 to 20 years ago and no arrest record since, it appears as if a person has cleaned up his life."

It could be argued that in Kusaba's case, the missing information wouldn't have mattered had he not been arrested again. But the ultimate decision to place a child rests with the adoption agency, which, under this scenario, risked operating on incomplete information.

In addition, Habbeshaw's record was never in question, though court records show she faced the same charges as her husband. Court archives fail to show what happened to her case after it was transferred from Davis County to Salt Lake County.

Debbie Jo Olsen, 3rd District Court clerk, doesn't rule out the possibility that the record was lost during the transfer, but says that's unlikely.

Often if an arrest or charges are old enough, Erickson said, BCI researchers will ask court clerks to dig into their archived files to determine how an arrest ended. Her four-person staff is always working to update spotty files.

"Our greatest focus is filling holes on felony arrests," said Erickson, stressing all dead-end background checks are researched, even for misde- meanors.

Stettler says, "If we're missing information, it's usually from the justice courts. No system is perfect. But we do what we can to avoid errors by checking for aliases and doing fingerprint searches on people with names like John Smith."